Micro Gear Efficiency
 

Many BMX bikes come with the tiny sprockets and cogs. Like 25/9 and such. Yet a bike can have essentially the same overall ratio with larger sprockets. Like 44/16 or such. Laboratory tests have shown that larger sprockets are more efficient. My question is assuming the same (or very close) final ratio, would you be able to "feel" the difference on a test ride of an otherwise identical bike? Or measure the difference riding a set course?

Have you ever actually tried this in real life? Thanks.

There is less drag over a larger cog and sprocket set - which is why a racing oriented BMX bike would utilize a physically larger set (like the 44/16 you mentioned) --

speed and pedaling efficiency take a backseat to clearance on a park bike however which is why you will see those smaller setups on the heavy freestyle and park oriented machines

But even with the final drive ratio being essentially the same, there will be marginally less resistance on a setup using a larger setup - but its enough to make a difference in a racing application

I don't ride BMX, but I turn pedals just the same. Yes you can absolutely feel a difference between a 52:26 and a 34:17. At higher power levels the difference is more obvious, so I often try to stay in the big or middle chainring as long as I can and drop to the smallest 'granny' gear only when I am out of other options. I believe this is because of two reasons - a smaller gearset puts more tension in the chain, and the chain links must move through a tighter angle coming off of and going on to smaller gears than bigger ones.

But, as mentioned above, depending on the type of riding you want to do, clearance is more important than efficiency.